The Ultra Wideband Blog

More about .11n

Pre-N and now Draft N 802.11 implementations have been on the market for several months now, long enough for people to begin testing them in earnest.  A recent – and very thorough – set of tests was just published by Anandtech.

What they found was that performance was mixed, and that there were a number of nagging problems with the implementations:

In our preliminary mixed mode testing we experienced the "bad neighbor" effect several times. Not only with our own internal 802.11g network but also visits from actual neighbors who were upset with having to constantly reboot their systems during our testing phase.

In addition, Anandtech observed:

We would notice stutters when saving large files to the network or trying to stream compressed (DivX) video from our server.

Many of our customers have also been testing .11n for use in video distribution in consumer electronics devices.  What they’ve found is similar to the results reported in the Anandtech article.  And in particular, these customers are continuing to prove to themselves that WiFi in any flavor isn’t suitable for video.  Some have gone as far as to build prototypes and take them to tradeshows only to have them fail onsite.

For the full report on 802.11n, visit the Anandtech site.

Compression Question

Why does wireless video networking – even with UWB – require compression? It’s a good question. The 1080i displays of today require a huge data stream of 1.87 Gbps. Without compression, you wouldn’t be able to distribute video wirelessly. So what video compression is best? That’s a more difficult question to answer. Perhaps there is no one right answer. All compression technologies strive for the lowest possible data rate while preserving the highest quality, error free picture. JPEG2000 is one choice. It has advantages because of its intra-frame compression scheme. MPEG-4 and MPEG-2 are also widely used because of their coding efficiencies.

Tzero and Analog Devices chose to use JPEG2000 in the companies' wireless HDMI reference design. There are a number of advantages for JPEG2000 today, and those are covered in a new whitepaper and DesignLine article.  Other advantages will emerge as display technology advances to 1080p and beyond.  For instance, compression schemes like MPEG-2 become less and less efficient as resolutions increase. An independent study conducted as part of the PULSERS EC Integrated Project investigated compression alternatives for wireless systems for high-speed short-range video transmissions. This study concluded that for equivalent video quality (defined as visually lossless), H.264 requires 39.6% more data, MPEG-4 requires 53.5% more data and MPEG-2 requires 150% more data. Visit the PULSERS website for more information.

This isn’t an argument for one compression technology or another. Manufacturers and service providers need to make their own decisions. And UWB has no restriction on what can be used over its high-speed links. Which compression do you think will win out for wireless video?

Wireless HDMI

One of the biggest hidden costs when purchasing a high-definition television is the cost of the required HDMI cabling. For even their shortest cables, some manufacturers charge more than $200.  And hiding that cable in a wall can run into the thousands of dollars. Tzero and Analog Devices have teamed up to address that problem with a reference design aimed at consumer electronics companies. It uses Tzero's ultra wideband technology and Analog Devices JPEG2000 compression chipset.That solution should help get a range of devices with wireless video capabilities rapidly to market.  Read the announcement.